Constant Phase Shift Research Articles

Capability of different multiaxial fatigue evaluation approaches on adhesively butt-bonded hollow cylinders under multiaxial loading with variable amplitudes

Currently, there is a lack of reliable approaches for the fatigue assessment of adhesively bonded joints that are subject to multiaxial stresses with variable amplitudes. To improve the current situation, investigations are made on the capability of three multiaxial evaluation approaches based on fatigue tests of adhesively butt-bonded hollow cylinders under multiaxial loading with constant phase shift and variable amplitudes.The investigated approaches are the Gough-Pollard criterion, the Findley criterion and a new method presented here, which is based on a multiaxial counting method and an invariant equivalent stress hypothesis (MCES-Method).While the Gough-Pollard criterion has a low computational effort, it does not reflect the fatigue life extending effect due to a phase shift without using a fitting parameter that is not physically based. The Findley criterion is less suitable for the investigated multiaxial stress states (with and without phase shift), although the fatigue life prediction under these load conditions is at least conservative. The MCES-Method has the highest accuracy of the methods considered. By combining research findings from published papers in the context of adhesively bonded joints, all investigated load scenarios are estimated with high prognosis quality.

Surface profile inspection for large structures with laser scanning

Fringe projection profilometry is a powerful tool that is widely applied to shape measurement of objects in engineering. Limited by the light intensity of the projection unit, this technique is difficult to be applied to surface inspection of large structures, especially in outdoor applications. In this study, a line laser source is selected as the light projection unit. The line laser beam is controlled to scan the surface with the predefined angular speed while a stationary imaging unit captures images. An image fusion strategy has been proposed to construct grating images with a constant phase shift, which facilitates full-field phase shifting in determination of the structural profile. The accuracy of the measurement method is discussed and compared with a commercial 3D laser scanner. The proposed technique has also been applied to the surface topography of the wind turbine blades. The experimental results show that the bulging defects on the surface of the wind turbine blade model are detectable, which shows the feasibility of the proposed method in characterization of surface profile on large structures.

Diffractive Sail-Based Displaced Orbits for High-Latitude Environment Monitoring

This paper analyzes the possibility of maintaining a circular displaced non-Keplerian orbit around the Sun by means of a Sun-facing diffractive sail. With the goal of monitoring the Earth’s high-latitude regions, the spacecraft is required to track its displaced orbit at an angular velocity equal to the mean motion of the planet. In doing so, the spacecraft keeps a constant average phase shift with respect to Earth’s angular position along its orbit, allowing the objectives of the scientific mission to be achieved. The diffractive sail, recently proposed by Swartzlander and chosen in this paper as the spacecraft’s primary propulsion system, is a special photonic solar sail in which the membrane film is covered by an advanced diffractive metamaterial. In particular, a Sun-facing diffractive sail with a grating at normal incidence generates radial and transverse thrust components of equal magnitude; that is, the thrust vector is tilted 45 degrees from the Sun-spacecraft line. This peculiarity enables the diffractive sail to maintain a family of circular displaced non-Keplerian orbits, each of which is characterized by unique values of radius and a lightness number for an assigned value of spacecraft displacement relative to the Ecliptic. A comparison with the ideal reflecting sail shows that the diffractive sail performs better because for the same overall spacecraft mass, the latter needs about 30% less surface area exposed to the Sun. Finally, this paper discusses the classical stability problem, assuming an error in orbit insertion of the diffractive sail-based spacecraft. In this context, extensive numerical simulations show that such displaced orbits are marginally stable.

Single-layer symmetrical full-port quasi-absorptive filtering phase shifter

In this article, a single-layer symmetrical full-port quasi-absorptive filtering phase shifter is presented. The proposed phase shifter is composed of a main quasi-absorptive filtering branch, a reference quasi-absorptive filtering branch, and two delay lines. The proposed phase shifter achieves both phase controlling function and quasi-absorptive filtering function for the first time. Each quasi-absorptive filtering branch can realize the quasi-absorptive filtering function. Meanwhile, the constant phase shift can be obtained by combining the two quasi-absorptive filtering branches and the two delay lines. The design formulas can be derived from the even- and odd-mode network analysis, and then two quasi-absorptive filtering phase shifters can be devised easily and quickly. For verification, a 90° quasi-absorptive filtering phase shifter, which is critical for circularly polarized antenna systems, is simulated, manufactured, and measured.

INVESTIGATION OF THE METHOD OF AUTOMATIC COMPENSATION OF TREND COMPONENTS OF PHASE SIGNALS IN SYSTEMS OF PHASE-METRIC CONTROL OF GEODYNAMIC PROCESSES

Geodynamic monitoring is widely used to monitor and control the state of various objects, as well as to detect and evaluate their changes over time. The software and hardware systems that implement it for tracking the geodynamics of objects over long time intervals should effectively highlight the trend component in the processed data. A promising way to implement geodynamic monitoring is the use of phasemetric methods of geoelectric control. The block diagram of the phase change detection path using these methods contains a differential amplifier, a phase detector, a low-pass filter, and a highly stable reference oscillator. To eliminate an undesirable constant phase shift based on this method, it is proposed to use an automatic compensation method that allows the system phase to be adjusted automatically in real time. The result of using the auto compensator is the formation of a "new" reference signal for the phase detector, excluding the formation of these phase shifts in its output signal. To illustrate the proposed approach, the use of software implementation of automatic compensation of unwanted shifts to identify a trend in phase signals obtained during geodynamic monitoring of the near-foundation zone of a structure is considered, which has shown its effectiveness and the possibility of further practical use.

Design of Electrostatic Aberration Correctors for Scanning Transmission Electron Microscopy.

In a scanning transmission electron microscope (STEM), producing a high-resolution image generally requires an electron beam focused to the smallest point possible. However, the magnetic lenses used to focus the beam are unavoidably imperfect, introducing aberrations that limit resolution. Modern STEMs overcome this by using hardware aberration correctors comprised of many multipole elements, but these devices are complex, expensive, and can be difficult to tune. We demonstrate a design for an electrostatic phase plate that can act as an aberration corrector. The corrector is comprised of annular segments, each of which is an independent two-terminal device that can apply a constant or ramped phase shift to a portion of the electron beam. We show the improvement in image resolution using an electrostatic corrector. Engineering criteria impose that much of the beam within the probe-forming aperture be blocked by support bars, leading to large probe tails for the corrected probe that sample the specimen beyond the central lobe. We also show how this device can be used to create other STEM beam profiles such as vortex beams and probes with a high degree of phase diversity, which improve information transfer in ptychographic reconstructions.

Effects of echo phase on bottlenose dolphin jittered-echo detection.

The ability of bottlenose dolphins to detect changes in echo phase was investigated using a jittered-echo paradigm. The dolphins' task was to produce a conditioned vocalization when phantom echoes with fixed echo delay and phase changed to those with delay and/or phase alternated ("jittered") on successive presentations. Conditions included: jittered delay plus constant phase shifts, ±45° and 0°-180° jittered phase shifts, alternating delay and phase shifts, and random echo-to-echo phase shifts. Results showed clear sensitivity to echo fine structure, revealed as discrimination performance reductions when jittering echo fine structures were similar, but envelopes were different, high performance with identical envelopes but different fine structure, and combinations of echo delay and phase jitter where their effects cancelled. Disruption of consistent echo fine structure via random phase shifts dramatically increased jitter detection thresholds. Sensitivity to echo fine structure in the present study was similar to the cross correlation function between jittering echoes and is consistent with the performance of a hypothetical coherent receiver; however, a coherent receiver is not necessary to obtain the present results, only that the auditory system is sensitive to echo fine structure.

Bandstructure of phononic crystal of rotating heterogeneous cylinders: Time periodicity due to pure mechanical modulation

Existing designs of elastic spatiotemporal periodic structures usually require electric/piezoelectric elements that provide temporal modulation of elastic properties. While this method has advantages in many aspects, it usually allows relatively low modulation depth. Here we propose a design for spatiotemporal elastic media that is experimentally feasible, involves pure mechanical elements, and may provide any desired temporal modulation depth. In our scheme the scatterers of a phononic crystal are cylinders composed of two (or more) semi-cylinders (parts) of different materials. The cylinders are capable for rotation with high speed in a stationary fluid environment that provides time-dependent medium for propagating sound wave. Adjusting the elastic contrast between the materials of solid semi-cylinders the necessary modulation depths can be achieved. Different regimes of temporal modulation, from adiabatic to rapid oscillations can be realized by varying the frequency of rotation. We report momentum/energy gaps and other features of the bandstructure that are theoretically obtained using plane wave expansion. Nonreciprocal effects are studied for a phononic crystal with a square unit cell containing two heterogeneous cylinders rotating synchronically with a constant phase shift. [This work is supported by the NSF under EFRI Grant No. 1741677.]

Common DC-Link Capacitor Harmonic Current Minimization for Cascaded Converters by Optimized Phase-Shift Modulation

This paper investigates the influence of a constant carrier phase shift on the DC-link capacitor harmonic current of cascaded converters used in fuel-cell and mild-hybrid electric vehicles. In these applications, a DC-DC converter can be adopted between the battery and the motor drive inverter in a cascaded structure, where the two converters share the same DC-link. Since the DC-link capacitor of such a system represents a critical component, the optimization of the converter operation to limit the current stress and extend the lifetime of the capacitor is an primary objective. This paper proposes the use of a carrier phase shift between the modulations of the two converters in order to minimize the harmonic current of the DC-link capacitor. By harmonic analysis, an optimal carrier phase shift can be derived depending on the converter configuration. Analytical results are presented and validated by hardware-in-the-loop experiments. The findings show that the pulse width modulation carrier phase shift between the interleaved boost converter and the voltage source motor drive inverter has a significant influence on the DC-link capacitor current and thus on its lifetime. A case study with two-cell and three-cell interleaved boost converters shows a possible DC-link capacitor lifetime extension of up to 390%.

Analytical Solutions for Double-Slit Diffraction with Constant Phase Shift

Analytical Solutions for Double-Slit Diffraction with Constant Phase Shift

On Practical RIS-Aided OFDM With Index Modulation

Reconfigurable intelligent surface (RIS)-aided communication has been regarded as one of the promising technologies for future wireless networks with regards to controlling the propagation environment and enhancing the quality of the end-to-end communication links. In this study, considering the importance of index modulation (IM) and RIS-aided schemes in 6G networks, first, an RIS-aided orthogonal frequency division multiplexing (OFDM)-IM system design is proposed. Previous studies focusing on RIS-aided OFDM systems are based on an ideal reflection model, where the constant amplitude and variable phase shift of the RIS are independent of the frequency of the incoming signal. However, in realistic applications, this ideal RIS model may not be accurate since both the phase shift and amplitude of RIS elements depend on the frequency, which makes their effect significant, especially for wideband systems. Therefore, this study primarily considers a practical RIS model through designing the RIS reflection coefficients for OFDM-IM systems. In order to further enhance the bit error rate (BER) performance of the RIS-aided OFDM-IM system, an exhaustive search-based optimization algorithm that maximizes the average minimum Euclidean distance (AMED) within the subblocks is also proposed. Moreover, extensive computer simulation results are produced in order to illustrate the performance improvement of the proposed algorithm over the reference algorithms in the literature. The proposed AMED-based reflection coefficient design algorithm provides better BER performance for RIS-aided OFDM-IM systems concerning the presented algorithms.

Motion-resistant structured illumination microscopy based on principal component analysis.

Structured illumination microscopy (SIM) has become one of the most significant super-resolution techniques in bioscience for observing live-cell dynamics, thanks to fast full-field imaging and low photodamage. However, artifact-free SIM super-resolution reconstruction requires precise knowledge about variable environment-sensitive illumination parameters. Conventional algorithms typically, under the premise of known and reliable constant phase shifts, compensate for residual parameters, which will be easily broken by motion factors such as environment and medium perturbations, and sample offsets. In this Letter, we propose a robust motion-resistant SIM algorithm based on principal component analysis (mrPCA-SIM), which can efficiently compensate for nonuniform pixel shifts and phase errors in each raw illumination image. Experiments demonstrate that mrPCA-SIM achieves more robust imaging quality in complex, unstable conditions compared with conventional methods, promising a more compatible and flexible imaging tool for live cells.

Effect of particle regularity on the shear response of geogrid-granular material interface under cyclic normal loading

The investigation of shear behaviour on geogrid-granular material interface under cyclic normal loading (CNL) is significant in seismic design of reinforcement structure. The cyclic shear mechanism about the effect of particle overall regularity on reinforced soil interface was analysed using dynamic direct shear apparatus. Five mixtures of round spherical media and crushed limestone with different percentages were selected to obtain various particle overall regularity. By comparing the shear behaviour under various overall regularity, the interface shear stress and vertical displacement under the CNL condition were smaller than those under the static loading condition. The decrement in interface shear stress of lower overall regularity was smaller than that of higher overall regularity. The interface peak shear stress, final vertical displacement decreased with the increase of cyclic normal loading amplitude and overall regularity. The effect of initial normal loading on ratio of strength reduction and energy consumption was reverse to that of the overall regularity. Based on the constant relative phase shift of the peak normal stress and friction coefficient for various overall regularity, the prediction formula was proposed. The test results improve the understanding on how normal loading perturbations and particle overall regularity affect the shear behaviour of reinforced soil interface.

Secrecy Rate Analysis of Randomized Radiation for Intelligent Reflecting Surface-Aided Communication Systems

We consider an intelligent reflecting surface (IRS)-assisted communication system as a cost-effective technique to enhance secrecy rate performance in physical-layer security (PLS) systems. In this letter, the randomized radiation (RR)-based PLS algorithm, which uses active antenna arrays to randomize the radiation pattern, is adopted in IRS through passive beamforming. We show that RR cannot be simply applied to IRS because the secrecy rate is subject to the phase-dependent amplitude variations in IRS. Therefore, we provide an exact and closed-form expression for the secrecy rate of RR using IRS. Based on the analysis, we introduce a constant phase shift into the IRS elements and identify it as a key parameter to optimize the secrecy performance through a genetic algorithm.

Analysis and Simulation of Overmodulation Modes of a Three-Inverter Block of the Photovoltaic Installation

The purpose of this work is to modernize the control scheme of a transformer-based photovoltaic system with three inverters controlled by the modified algorithms of synchronous spacevector PWM in order to ensure linear regulation of the system in the overmodulation zone of the inverter block in the process of forming a symmetrical and synchronized (with the operating frequency of the system) voltage on the inverter-side windings of a power transformer. This goal is achieved by the fact that the process of two-stage control of the system in the zone of overmodulation of inverters is carried out on the basis of synchronized phase shifts between the control signals of inverters (a constant phase shift, as well as an additional adjustable phase shift between the inverter signals as a function of the duration of clock subintervals), with an appropriate modification of the algorithms of synchronous PWM of inverters due to the inclusion of two specialized correction factors in the basic functional dependencies. The most significant results of the work include the fact that in a system with a modified control scheme and modulation of the inverter block in the overmodulation zone, the resulting voltage on the inverter-side windings of the power transformer is characterized by quarterwave symmetry, and its spectrum contains no even-order harmonics, as well as subharmonics, including regimes of fluctuations in the operating frequency of the system connected to a three-phase network, thereby helping to reduce losses in the transformer windings and improve the efficiency of photovoltaic systems.

Antenna Selection Based on Matching Theory for Uplink Cell-Free Millimetre Wave Massive Multiple Input Multiple Output Systems

In this paper, we propose a hybrid beamforming architecture with constant phase shifters (CPSs) for uplink cell-free millimetre-wave (mm-Wave) massive multiple-input multiple-output (MIMO) systems based on exploiting antenna selection to reduce power consumption. However, current antenna selection techniques are applied for conventional massive MIMO, not cell-free massive MIMO systems. Therefore, the enormous computational complexity of these techniques to optimally select antennas for cell-free massive MIMO networks is caused by numerous randomly distributed access points (APs) in the service area and their large antennas. The architecture proposed in this work solves this issue by employing a low-complexity matching technique to obtain the optimal number of antennas, chosen based on channel magnitude and by switching off antennas that contribute more to interference power than to desired signal power for each radio frequency (RF) chain at each AP, instead of assuming all RF chains at each AP have the same number of selected antennas. Therefore, an assignment optimization problem based on a bipartite graph is formulated for cell-free mm-Wave massive MIMO system uplinks. Then, the Hungarian method is proposed to solve this problem due to its ability to solve this assignment problem in a polynomial time. Simulated results show that, despite several APs and antennas, the proposed matching approach is more energy-efficient and has lower computational complexity than state-of-the-art schemes.

Fast and pure phase-shifting off-axis holographic microscopy with a digital micromirror device.

We present a phase-shifting digital holographic microscopy technique, where a digital micromirror device enables to perform a precise phase-only shift of the reference wave. By coupling the beam into a monomode fiber, we obtain a laser mode with a constant phase shift, equally acting on all pixels of the hologram. This method has the advantage of being relatively simple and compatible with high frame rate cameras, which makes it of great interest for the observation of fast phenomena. We demonstrate the validity of the technique in an off-axis configuration by imaging living paramecia caudata.

Ground-roll extraction using the Karhunen-Loeve transform in the time-frequency domain

Ground-roll suppression is critical for seismic reflection data processing. Many standard methods, i.e., f-k fan filtering, fail when spatially aliased surface wave interference is present in the data. Spatial aliasing is a common problem; receiver spacing is often not dense enough to extract wavenumbers of low-velocity surface waves. It has long been known that the Karhunen-Loeve (KL) transform can be used to suppress aliased ground roll. However, the ground roll should be flattened before suppression, which is challenging due to the dispersion of surface wave velocities. I propose to solve this problem via the time-frequency domain. I apply the S-transform, which was previously shown to perform well in the multichannel analysis of surface waves. A simple complex-valued constant phase shift is a suitable model of surface wave propagation in common-frequency S-transform gathers. Therefore, it is easy to flatten the corresponding S-transform narrow-band frequency surface wave packet and extract it from the data by principal component analysis of the corresponding complex-valued data-covariance matrix. As the result, our S-transform KL (SKL) method filters the aliased ground roll without damaging the reflection amplitudes. The advantages of SKL filtering have been confirmed by synthetic- and field-data processing.

Effect of acoustic diffraction phase shift on caustic structure in deep sea convergence zone

The constant phase shift <inline-formula><tex-math id="M1">\begin{document}$- {{\text{π}}}/{2}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="20-20220763_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="20-20220763_M1.png"/></alternatives></inline-formula> generated by a turning point is an ideal approximation under high frequency conditions. In fact, when sound waves pass through a turning point, it will travel horizontally for a certain distance in the form of inhomogeneous plane wave and then be refracted back. At this time, a functional phase shift should also be included at the turning point. In addition, a refracted ray will bring about reflection phase shift when the turning point is close to the waveguide edge. These two kinds of phase shifts which are associated with the diffraction phenomenon are called diffraction phase shifts in this paper and are more notable when the frequency goes down. In order to accurately obtain the caustic structure at low frequency, the diffraction phase shift is used to correct the classical ray theory in calculating ray skip distance, traveling time, and group velocity in this work. On this basis, a simple and explicit analytical model is proposed which is suitable for calculating the low frequency deep water caustics. The numerical study of the first upper convergence zone in the complete deep water sound channel shows that there are three caustic lines in the refracted-refracted (RR) convergence zone and four caustic lines in the refracted surface-reflected (RSR) convergence zone under the condition of high frequency hypothesis. When the diffraction phase shifts at low frequency are included, and compares with high frequency results, it is found that the horizontal beam displacement caused by the reflection phase shift will make the RR caustics horizontally move towards the source and also lead the RSR rays to generate several new caustics, while the beam displacement caused by sound propagating in the form of inhomogeneous plan wave will make the RR caustics horizontally move away from the sound source. Accompanied with the increased frequency, the diffraction effect will decrease, and the caustic structure gradually tends to the classical ray theory results. The reliability of the correction results is verified by the normal mode theory. The model proposed in this work makes up for the deficiency of classical ray theory.

Design Method of Constant Phase-Shifter Microwave Passive Integrated Circuit in 130-nm BiCMOS Technology With Bandpass-Type Negative Group Delay

The miniaturization and application development are the expected challenges on the today engineering design research on bandpass (BP) type negative group delay (NGD) circuit. To overcome this technical limit, an innovative contribution on integrated circuit (IC) design method of BP-NGD application to design constant phase shifter (PS) in 130-nm BiCMOS technology is developed in the present paper. The BP-NGD PS microwave passive IC is topologically consisted of cascade of CLC- and RLC-resonant networks. After the S-matrix modelling, the synthesis design equations enabling to calculate each lumped component values constituting the BP-NGD PS BiCMOS are established. The design equations are expressed knowing the targeted specifications as phase shift and operating frequency. The BiCMOS design methodology including the key steps as design rule checking (DRC), layout versus schematic (LVS) and post-layout simulation (PLS) is described. The miniaturized BP-NGD PS design feasibility is verified with schematic and layout simulations with IC CMOS standard commercial software tool. A proof-of-concept (POC) of 130-nm BiCMOS BP-NGD PS operating at the center frequency <i>f</i>₀=1.9 GHz and bandwidth &#x0394;<i>f</i>=0.1 GHz is designed and simulated. After DRC, the chip layout of miniaturized BP-NGD PS POC presents 0.407 mm&#x00B2; size. The BP-NGD PS POC exhibits constant phase shift notable value of about &#x03C6;₀=-90&#x00B0;+/-0.4&#x00B0; under <i>S</i>₂₁(<i>f</i>₀)=-6+/-1 dB transmission coefficient with good flatness and reflection coefficients (<i>S</i>₂₁(<i>f</i>₀) and <i>S</i>₂₁(<i>f</i>₀)) widely better than -10 dB. The design robustness is confirmed by 1000-trial Monte Carlo uncertainty analyses with PLS results. Because of the potential integration in wireless sensor networks (WSNs), the BP-NGD PS under study is a promising candidate for the improvement of the future 5G and 6G transceiver design.